Aryloxyphenoxy propionylthioureas which are useful as herbicides

ABSTRACT

Substituted aryloxyphenoxy propionyl thiourea compounds useful as herbicides, and their methods of use, a representative one of which has the structural formula   &lt;IMAGE&gt;   The method comprises applying the above referenced compound to the locus where control is desired.

BACKGROUND OF THE INVENTION

The present invention relates to certain substituted aryloxyphenoxy propionylthiourea herbicides which are particularly useful as post-emergent herbicides against annual and perennial grasses.

Herbicides are widely used by farmers, commercial agricultural companies, and other industries in order to increase crop yields for such staple crops as corn, soybeans, rice, and the like, and to eliminate weed growth along highways, railroad rights-of-way, and other areas. Herbicides are effective in killing or controlling unwanted weeds which compete for soil nutrients with the crop plants, and by reason of the fact that they kill weeds, are responsible for improving the aesthetic appearance of highway and railroad rights-of-way.

There are a number of different types of herbicides presently sold commercially, and these fall into two general categories. The categories are pre-emergence and post-emergence herbicides. The pre-emergence herbicides are normally incorporated into or applied to the soil prior to the emergence of the weed plants from the soil, and the post-emergence herbicides are normally applied to plant surfaces after emergence of the weeds or other unwanted plants from the soil.

THE PRIOR ART

The prior art contains numerous examples of substituted propionic acid-type compounds which have been disclosed to be herbicidally effective against grasses in particular, as compared to broad leaf weed pests. Examples of such prior art references include U.S. Pat. Nos. 4,200,587 and 4,325,729, both of which disclose propionic acid derivatives as being effective herbicides against grasses.

Efforts are constantly being made, however, to find compounds which are equal to or greater in effectiveness than presently existing compounds, or which are more economical to produce.

DESCRIPTION OF THE INVENTION

It has now been discovered that certain new and novel substituted aryloxyphenoxy propionylthiourea compounds have good herbicidal and plant growth regulating activity, particularly when applied as post-emergent herbicides and used against annual and perennial grasses.

As used herein, the term "herbicide" means a compound or composition which controls or modifies the growth of plants. By the term "herbicidally effective amount" is meant any amount of such compound or composition which causes a modifying effect upon the growth of plants. By "plants" is meant germinant seeds, emerging seedlings and established vegetation, including roots and above-ground portions. Such controlling or modifying effects include all deviations from natural development, such as killing, retardation, defoliation, dessication, regulation, stunting, tillering, leaf burn, dwarfing and the like.

The new and novel compounds of this invention are substituted aryloxyphenoxy propionylthioureas.

The preferred compounds have the formula ##STR2## wherein R₁ is CF₃ or halogen; R₂ is H or halogen; A is CH or N; R₃ and R₄ are each independently hydrogen or lower alkyl, alkenyl or alkynyl groups having up to 5 carbon atoms; and wherein R₃ and R₄ together optionally may form a ring system having from 4 to 6 carbon atoms.

The preferred compound is N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)-propionyl]-N-1,1-dimethyl propargyl thiourea.

Other useful compounds include, for example:

S-methyl N-methylaminocarbonyl, N'-[2-(4'-(5"-trifluoromethyl-2"-pyridyloxy)phenoxy)propionyl]isothiourea;

N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxyO-propionyl]N',N'-diallylthiourea;

N-[2-(4-(4"-trifluoromethylphenoxy)phenoxy)propionyl] N'-2,2-dimethylpropargyl;

N-[2-(4'-(5"-trifluoromethylpyridyl-2"-oxy)phenoxy)propionyl]N-methyl-N'-(1-methyl-2-propionyl)thiourea; and

N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)propionyl]N'-methyl-N'-(1-methyl-2-propynyl)thiourea.

The preferred compounds, as set forth above, have been found to have especially good herbicidal activity against perennial and annual grasses when applied as post-emergent herbicides. They are also effective as a pre-emergent herbicide and plant growth regulator, but not to the same extent as when applied post-emergent.

The compounds of the invention can be produced in a multi-step process in accordance with the following generalized sequence of steps. ##STR3## where R₁, R₂, R₃ and R₄ are as previously defined.

The end product compounds can be produced by selecting any one of the compounds produced in accordance with steps 1, 2 or 3 above and continuing the reaction sequence as indicated.

Examples 1-3 below illustrate various methods of making the compounds of the invention using various starting materials.

EXAMPLE 1 Preparation of N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)-propionyl]-N"-1,1-dimethylpropargyl thiourea

A reaction vessel was equipped with nitrogen atmosphere, and into this was charged 1.6 grams (g) oven-dried sodium thiocyanate dissolved in 50 milliliters (ml) of dry acetone. The solution was heated to dissolve the sodium thiocyanate and thereafter 6.9 g of 2-[4'-(4"-trifluoromethylphenoxy)phenoxy]-propionyl chloride acid chloride dissolved in 25 ml dry acetone was added. The mixture was stirred for approximately 20 minutes, at which time a white solid precipitated out of solution.

Thereafter, 1.9 g 2-amino-2-methylbutyne dried over magnesium sulfate dissolved in 25 ml of acetone was charged to the reaction mixture. This mixture was then stirred for 2 hours at room temperature. The acetone was then stripped off, and the deposit dissolved in 50 ml of water plus 50 ml of methyl chloride. The phases were separated and the organic phase was washed with 50 ml of 5% sodium hydroxide, 50 ml water, and 50 ml of 5% HCl, followed by 50 ml of water again. The solution was dried over magnesium sulfate, filtered and the solids stripped off.

There remained 7.8 g of an orange-brown oil. It was further purified by high pressure liquid chromatography (hplc). The product was identified by suitable analytical techniques as being the subject compound.

EXAMPLE 2 Preparation of N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)-propionyl]-N',N'-diallyl thiourea

Into a reaction vessel equipped with nitrogen atmosphere was charged 1.6 g oven-dried sodium thiocyanate and 30 ml of dry acetone. The solution was heated to dissolve the dried sodium thiocyanate. Thereafter, 6.9 g of the same acid chloride as in Example 1 was dropped in, and the solution heated for 30 minutes. A white solid fell out of solution. Next, 1.9 g diallylamine dissolved in 30 ml of dry acetone was added. At this point a slightly exothermic reaction occurred. The reaction mixture was stirred for 2 hours at room temperature. The reaction solution was then stripped of acetone, and the orange deposit dissolved in water and methyl chloride, 50 ml each. The organic phase was washed sequentially with saturated sodium bicarbonate, water, 5% NaOH, and water again.

The organic phase was then dried over magnesium sulfate, filtered, and the organic solvents stripped off.

There was obtained a yield of 5.8 g of an orange-yellow oil which upon further purification by hplc and being analayzed by suitable analytical techniques proved to be the subject compound.

EXAMPLE 3 Preparation of N-[2-(4'-(5"-trifluoromethylpyridyl-2"-oxy)phenoxy)-propionyl]-N'-methyl-N'-(1-methyl-propargyl)thiourea

Into a reaction vessel equipped with nitrogen atmosphere was added 1.2 g sodium thiocyanate and 25 ml acetone. The solution was heated to 30° to 40° C. to assure that the reagent was totally dissolved. Next, 2.6 g 2-[4'-(5"-trifluoromethylpyridyl-2"-oxy)phenoxy]propionyl chloride dissolved in 15 ml acetone was added and the solution was stirred for approximately 45 minutes. Following this 0.6 g 3-methylamino-1-butyne was added and the solution stirred for approximately 2 hours at room temperature. The solution was then stripped of the acetone, and the remaining product dissolved in a mixture of 50 ml water and 50 ml of methylene chloride and separated. The organic phase was then washed sequentially with 5% hydrogen chloride, water, 3% sodium hydroxide and water again. It was dried over magnesium sulfate, filtered, and the solvents stripped off.

An orange-yellow oil (5.7 g) was recovered, which was purified by hplc and was identified by suitable analytical techniques as being the subject compound.

EXAMPLE 4 Herbicidal Activity Tests

This example offers herbicidal activity test data to show the effectiveness of the compounds of the invention. The effect is observed by comparing the extent of weed control in test flats treated with the compounds against that occurring in similar control flats. The soil used in these tests was a sandy loam soil from the Livermore, Calif. area.

Also added to the soil was 17-17-17 fertilizer (N-P₂ O₅ -K₂ O on a weight basis), amounting to 50 ppm by weight with respect to the soil and 100 ppm Captan, a soil fungicide.

The treated soil was then placed in flats which were 3 inches deep, 6 inches wide, and 10 inches long. The soil was tamped and leveled with a row marker to impress six rows across the width of the flat. The test weeds were as follows:

    ______________________________________                                         COMMON NAME     SCIENTIFIC NAME ABR                                            ______________________________________                                         Broadleaf Weeds:                                                               annual morningglory                                                                            Ipomoea purpurea                                                                               AMG                                            cocklebur       Xanthium sp.    CB                                             hemp sesbania   Sesbania exaltata                                                                              SESB                                           velvetleaf      Abutilon theophrasti                                                                           VL                                             mustard         Brassica sp.    MD                                             nightshade      Solanum sp.     SP                                             pigweed         Amaranthus sp.  PW                                             Grasses:                                                                       yellow nutsedge Cyperus exculentus                                                                             YNS                                            downybrome      Bromus tectorum DB                                             foxtail         Setaria sp.     FT                                             annual ryegrass Lolium multiflorum                                                                             ARG                                            watergrass      Echinochloa crusgalli                                                                          WG                                             rox-orange sorghum                                                                             Sorghum bicolor SHC                                            wild oat        Avena fatua     WO                                             curly dock      Rumex crispus   CD                                             ______________________________________                                    

Crop plants were also planted at the same time. These were as follows:

    ______________________________________                                         CROP PLANTS    SCIENTIFIC NAME  ABR                                            ______________________________________                                         soybeans       Glycine max      SOY                                            rice           Oryzae sativa    RC                                             cotton         Gossypium hirsutum                                                                              COT                                            corn           Zea mays         CN                                             wheat          Triticum aestivum                                                                               WH                                             sorghum        Sorghum bicolor  ML                                             sugar beets    Beta vulgaris    SB                                             ______________________________________                                    

Sufficient seeds were planted to produce several seedlings per inch in each row. The flats were then placed in a greenhouse maintained at 70° to 85° F. (21° to 30° C.) and watered daily by sprinkler.

In the case of pre-emergent testing the herbicide was incorporated into the soil prior to planting of the seeds, at a rate equivalent to the indicated amounts in the Table.

In post-emergent testing chemical application is made by spraying 12 days after planting. The spray solution is prepared by dissolving 60 mg of herbicide compound in 20 ml of acetone containing 1% Tween® 20 (polyoxysorbitan monolaurate), then adding 20 ml of water to the resulting solution. The solution is sprayed at 80 gallon/acre, resulting in a 4 lb/acre rate of chemical application. Other rates were achieved by varying the solution concentration and/or the rate of spray.

In both instances, either pre- or post-emergent testing, approximately 12-14 days after treatment, the degree of weed control was estimated and recorded as percentage control compared to the growth of the same species in an untreated check flat of the same age. The rating scale ranges from 0 to 100%, where 0 equals no effect with plant growth equal to the untreated control, and 100 equals complete kill.

The results are listed in Tables I, II, and III below, each table representing a separated test sequence.

                                      TABLE I                                      __________________________________________________________________________     HERBICIDE TEST RESULTS                                                         Test Compound: N--[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)propionyl]-N'-     -1,1-dimethylpropargyl thiourea                                                __________________________________________________________________________     Application Percent Control Weeds                                              Rate (lb/A)                                                                           Method                                                                              YNS                                                                               DB FT ARG WG SHC                                                                               WO AMG CB SES                                                                               VL MD SP                                                                               PW                         __________________________________________________________________________     0.062  POST 0   0  80                                                                               25  100                                                                                80                                                                               45 0   0  0  0  0  0 0                          0.125  POST 0  20 100                                                                               40  100                                                                               100                                                                               65 0   0  0  0  0  0 0                          0.25   POST 0  35 100                                                                               70  100                                                                               100                                                                               85 0   0  0  0  0  0 0                          0.50   POST 0  50 100                                                                               80  100                                                                               100                                                                               90 0   0  0  0  0  0 0                          1.00   POST 0  80 100                                                                               90  100                                                                               100                                                                               100                                                                               0   0  20 20 20 0 0                          2.00   POST 0  85 100                                                                               100 100                                                                               100                                                                               100                                                                               25  0  35 40 30 0 35                         0.25   PRE  0  20  35                                                                                0   45                                                                                70                                                                                0 0   0  0  0  0  0 0                          0.50   PRE  0  35  70                                                                               50   95                                                                                95                                                                               40 0   0  0  0  0  0 0                          1.00   PRE  0  55  95                                                                               95  100                                                                               100                                                                               75 0   0  0  0  0  0 0                          2.00   PRE  0  95 100                                                                               100 100                                                                               100                                                                               100                                                                               0   0  0  0  0  0 0                          __________________________________________________________________________                           Application Percent Injury Crops                                               Rate (lb/A)                                                                           Method                                                                              SOY                                                                               RC COT                                                                               CN WH ML SB                         __________________________________________________________________________                           0.062  POST 0   90                                                                               0  80 40  80                                                                               0                                                0.125  POST 0   95                                                                               0  90 50  90                                                                               0                                                0.25   POST 0  100                                                                               0  95 55  95                                                                               0                                                0.50   POST 0  100                                                                               0  100                                                                               65 100                                                                               0                                                1.00   POST 25 100                                                                               20 100                                                                               90 100                                                                               30                                               2.00   POST 35 100                                                                               30 100                                                                               100                                                                               100                                                                               35                                               0.25   PRE  0   25                                                                               0  35  0  35                                                                               0                                                0.50   PRE  0   85                                                                               0  55  0  70                                                                               0                                                1.00   PRE  0   90                                                                               0  95  0 100                                                                               0                                                2.00   PRE  0   95                                                                               0  100                                                                               50 100                                                                               0                          __________________________________________________________________________

                                      TABLE II                                     __________________________________________________________________________     Application                                                                    Test     Rate                                                                  Cmpd.                                                                              Method                                                                              (lb/A)                                                                             DB FT ARG WG SHC                                                                               WO  BSG                                                                               AMG SESB                                                                               VL                                 __________________________________________________________________________     1   PES. 2.0 100                                                                               100                                                                               100 100                                                                               100                                                                               85  100                                                                               0   0   0                                      PES. 0.25                                                                               90 100                                                                               60   95                                                                                90                                                                               0   90 N   N   N                                      PES. 0.1 15  70                                                                                0   0  20                                                                               0   85 N   N   N                                      POST.                                                                               2.0 100                                                                               100                                                                               100 100                                                                               100                                                                               100 100                                                                               0   0   0                                      POST.                                                                               0.25                                                                               100                                                                               100                                                                               85  100                                                                               100                                                                               85  100                                                                               N   N   N                                      POST.                                                                               0.1 95 100                                                                               65  100                                                                               100                                                                               70  100                                                                               N   N   N                                  2   POST.                                                                               2.0 N  N  N   N  N  N   N  N   N   N                                      POST.                                                                               0.5 100                                                                               100                                                                               100 100                                                                               100                                                                               100 100                                                                               N   N   N                                      POST.                                                                               0.25                                                                               50  85                                                                               80  100                                                                               100                                                                               65  98 N   N   N                                      POST.                                                                               0.1  0  85                                                                               30    98                                                                              100                                                                               0   98 N   N   N                                      POST.                                                                               0.05                                                                                0  30                                                                               10   55                                                                                65                                                                               0   15 N   N   N                                      PES. 2.0 N  N  N   N  N  N   N  N   N   N                                      PES. 0.5 80 100                                                                               99  100                                                                               100                                                                               0   97 N   N   N                                      PES. 0.25                                                                                0  85                                                                                0   25                                                                                55                                                                               0   65 N   N   N                                      PES. 0.1  0  35                                                                                0   25                                                                                0 0   60 N   N   N                                      PES. 0.05                                                                                0  0  0   0  0 0   20 N   N   N                                  3   PES. 0.25                                                                               15  30                                                                                0   99                                                                                95                                                                               0   98 0   0   0                                      POST.                                                                               0.25                                                                               97 100                                                                               95  100                                                                               100                                                                               100 100                                                                               0   0   0                                  __________________________________________________________________________     Application                                                                    Test     Rate                                                                  Cmpd.                                                                              Method                                                                              (lb/A)                                                                             SP MD YNS                                                                               CB SOY                                                                               WH  ML RC SBH                                                                               CN COT                                __________________________________________________________________________     1   PES. 2.0 0  0  0  0  0  50  100                                                                               100                                                                               0  95 0                                      PES. 0.25                                                                               N  N  0  N  0  0   85 80 0  15 0                                      PES. 0.1 N  N  0  N  0  0   20  0 0  15 0                                      POST.                                                                               2.0 0  0  0  0  30 100 100                                                                               100                                                                               0  100                                                                               0                                      POST.                                                                               0.25                                                                               N  N  0  N  10 75  100                                                                               95 0  100                                                                               0                                      POST.                                                                               0.1 N  N  0  N  15 30  30 35 0  90 0                                  2   POST.                                                                               2.0 N  N  N  N  N  N   N  N  N  N  N                                      POST.                                                                               0.5 N  N  0  N  0  75  100                                                                               90 0  100                                                                               0                                      POST.                                                                               0.25                                                                               N  N  0  N  0  60  80 75 0  100                                                                               0                                      POST.                                                                               0.1 N  N  0  N  0  0   40 40 0  100                                                                               0                                      POST.                                                                               0.05                                                                               N  N  0  N  0  0   40 40 0  100                                                                               0                                      PES. 2.0 N  N  N  N  N  N   N  N  N  N  N                                      PES. 0.5 N  N  0  N  0  0   98 30 0  15 0                                      PES. 0.25                                                                               N  N  0  N  0  0   70 50 0  20 0                                      PES. 0.1 N  N  0  N  0  0   25 20 0   0 0                                      PES. 0.05                                                                               N  N  0  N  0  0    0  0 0   0 0                                  3   PES. 0.25                                                                               0  0  0  0  0  0   90 70 0  65 0                                      POST.                                                                               0.25                                                                               0  0  0  0  0  80  97 65 0  100                                                                               0                                  __________________________________________________________________________      N = Not evaluated.                                                             1 =                                                                            N--[2(4(4trifluoromethylphenoxy)phenoxy)propionylN',N'--diallylthiourea        2 =                                                                            N--[2(4(4trifluoromethoxyphenoxy)phenoxy)propionylN'--1,1diamethylproparg      3 = N--[2(4(5trifluoromethylpyridyl-2oxy)phenoxy)propionylN'--methylN'--       (1methyl-2-propinyl) thiourea                                            

                  TABLE III                                                        ______________________________________                                         Test Compound:                                                                 S--methyl N--methylaminocarbonyl N'--[2-(4'-(5"-trifluoro-                     methyl-2"-pyridyloxy)phenoxy)propionyl] isothiourea                                  Applica-                                                                 Cmpd. tion Rate                                                                No.   (lb/A)   GG     BSG  TF   RCM9  WO   COT  CN                             ______________________________________                                         4      1/16    40     10   0    10    0    0     0                                   1/8      50     30   0    30    0    0    30                                   1/4      70     50   20   60    30   0    60                             ______________________________________                                    

EXAMPLE 5

A postflood-postemergence test was performed in a simulated rice paddy as follows:

Plastic tubs measuring 10×7.5×5.75 inches (25.4×19.0×14.6 centimeters (cm)) were filled to a depth of 2 inches (5.1 cm) with 8 pounds (3.6 kilograms (kg)) of a loamy sand soil, containing 100 parts per million (ppm) of cis-N[(trichloromethyl)thio]-4-cyclohexene-1,2-dicarboximide (a commercial fungicide designated as Captan®) and 200 ppm of 18-18-18 fertilizer (containing 18% N, 18% P₂ O₅, and 18% K₂ on a weight basis). One pint (0.47 liter) of the soil was removed, the remaining soil was leveled and several rows were impressed across the width of the flat. Yellow nutsedge tubers (Cyperus esculentus), and seeds of annual morning glory (Ipomoea purpurea), sesbania (Sesbania sp.), and rice (Oryza sativa) were planted in separate rows. The pint of soil was then used to place a 0.5 inch (1.27 cm) layer over the seeds and tubers. The planted soil was placed in a greenhouse, and irrigated by sprinkling as needed to keep the soil moist. One to three days after the initial seeding another row was impressed 0.5 inches (1.27 cm) deep across the width of the flat and seeds of watergrass (Echinochloa crusgalli) were planted and covered by pinching together with the soil on either side of the seeder row. Seven to ten days after the original seeding, the soil was flooded with 2 inches (5.1 cm) of water. At flooding time the grass species were in the two leaf stage 1 to 2 inches (2.54 to 5.1 cm) high and the nutsedge was 1 inch (2.54 cm) high.

Test compounds or combinations were then applied by pipeting 5.0 milliliters (ml) of a stock solution of appropriate concentration into the flood water to produce the desired application rate in pounds of active ingredient per acre (lb/A) or its equivalent in kilograms per hectare (kg/ha). For the particular tubs used, 5.5 milligrams (mg) of active ingredient per tub is equivalent to 1.0 lb/A.

The tubs were allowed to stand for three weeks after the application of the test compounds and water was added as needed to maintain the water level. At the end of 3 weeks, the species were rated visually as percent control from 0 to 100%, where 0% represents no injury and 100% represents complete kill when compared to an untreated check tub. The percent control was based on the total injury to the plants due to all factors.

                  TABLE IV                                                         ______________________________________                                         Post-Flood Application                                                         Test. Application                                                              Cmpd. Rate (lb/A)                                                                               WG      AMG   SESB   YNS  RC                                  ______________________________________                                         1     2.0        100     0     20     10   100                                       4.0        100     0     20     10   100                                       1.0        100     0     0      0    100                                       2.0        100     0     0      0    100                                       1.0        100     0     0      0    100                                       2.0        100     20    20     0    100                                 2     2.0        100     0     0      0    90                                        4.0        100     0     0      0    95                                        1.0        100     0     0      0    90                                        2.0        100     0     0      0    95                                        1.0        100     20    0      0    95                                        2.0        100     0     0      0    100                                 3     2.0        100     0     30     0    95                                        4.0        100     0     0      0    100                                       2.0        100     0     30     0    95                                        4.0        100     0     0      0    100                                 4     2.0        100     0     0      0    60                                        4.0        100     0     0      0    50                                         0.25       30     0     0      0     0                                        0.5         55     0     0      0    15                                        1.0         80     0     0      0    70                                        1.0         75     0     0      0    85                                        2.0        100     0     0      0    90                                        1.0        100     0     0      0    95                                        2.0        100     0     0      0    100                                 ______________________________________                                          1 =                                                                            N--[2(4(4trifluoromethylphenoxy)phenoxy)propionylN',N'--diallylthiourea        2 =                                                                            N--[2(4(4trifluoromethoxyphenoxy)phenoxy)propionylN'--1,1dimethylpropargy      3 =                                                                            N--[2(4(5trifluoromethylpyridyl-2oxy)phenoxy)propionylN'--methylN'--(1met     yl-2-propinyl) thiourea                                                         4 = S--methyl N--methylaminocarbonyl                                           N'--[2(4(5trifluoromethyl-2pyridyloxy)phenoxy)propionyl]isothiourea      

METHODS OF APPLICATION

The herbicidal compositions of the present invention are useful in controlling the growth of undesirable vegetation by pre-emergence or post-emergence application to the locus where control is desired, including pre-plant and post-plant soil incorporation as well as surface application. The compositions are generally embodied in formulations suitable for convenient application. Typical formulations contain additional ingredients or diluent carriers which are either inert or active. Examples of such ingredients or carriers are water, organic solvents, dust carriers, granular carriers, surface active agents, oil and water, water-oil emulsions, wetting agents, dispersing agents, and emulsifying agents. The herbicidal formulations generally take the form of dusts, emulsifiable concentrates, granules and pellets, or microcapsules.

A. DUSTS

Dusts are dense powder compositions which are intended for application in dry form. Dusts are characterized by their free-flowing and rapid settling properties so that they are not readily windborne to areas where their presence is not desired. They contain primarily an active material and a dense, free-flowing, solid carrier.

Their performance is sometimes aided by the inclusion of a wetting agent, and convenience in manufacture frequently demands the inclusion of an inert, absorptive grinding aid. For the dust compositions of this invention, the inert carrier may be either of vegetable or mineral origin, the wetting agent is preferably anion or nonionic, and suitable absorptive grinding aids are of mineral origin.

Suitable classes of inert solid carriers for use in the dust compositions are those organic or inorganic powders which possess high bulk density and are very free-flowing. They are also characterized by low surface area and poor liquid absorptivity. Suitable grinding aids are natural clays, diatomaceous earths, and synthetic mineral fillers derived from silica or silicate. Among ionic and nonionic wetting agents, the most suitable are the members of the group known to the art as wetting agents and emulsifiers. Although solid agents are preferred because of ease of incorporation, some liquid nonionic agents are also suitable in the dust formulations.

Preferred dust carriers are micaceous talcs, pyrophyllite, dense kaolin clays, tobacco dust and ground calcium phosphate rock.

Preferred grinding aids are attapulgite clay, diatomaceous silica, synthetic fine silica and synthetic calcium and magnesium silicates.

Most preferred wetting agents are alkylbenzene and alkyl-naphthalene sulfonates, sulfated fatty alcohols, amines or acid amides, long chain acid esters of sodium isothionate, esters of sodium sulfosuccinate, sulfated or sulfonated fatty acid esters, petroleum sulfonates, sulfonated vegetable oils, and ditertiary acetylenic glycols. Preferred dispersants are methyl cellulose, polyvinyl alcohol, lignin sulfonates, polymeric alkylnaphthalene sulfonates, soldium naphthalenesulfonate, polymethylene bisnaphthalenesulfonate, and sodium-N-methyl-N-(long chain acid)taurates.

The inert solid carriers in the dusts of this invention are usually present in concentrations of from about 30 to 90 weight percent of the total composition. The grinding aid will usually constitute 5 to 50 weight percent of the compositions, and the wetting agent will constitute from about 0 to 1.0 weight percent of the composition. Dust compositions can also contain other surfactants such as dispersing agents in concentrations of up to about 0.5 weight percent, and minor amounts of anticaking and antistatic agents. The particle size of the carrier is usually in the range of 30 to 50 microns.

B. EMULSIFIABLE CONCENTRATES

Emulsifiable concentrates are usually solutions of the active materials in nonwater-miscible solvents together with an emulsifying agent. Prior to use, the concentrate is diluted with water to form a suspended emulsion of solvent droplets.

Typical solvents for use in emulsifiable concentrates include weed oils, chlorinated hydrocarbons, and nonwater-miscible ethers, esters, and ketones.

Typical emulsifying agents are anionic or nonionic surfactants, or mixtures of the two. Examples include long-chain alkyl or mercaptan polyethoxy alcohols, alkylaryl polyethoxy alcohols, sorbitan fatty acid esters, polyoxyethylene ethers with sorbitan fatty acid esters, polyoxyethylene glycol esters with fatty or rosin acids, fatty alkylol amide condensates, calcium and amine salts of fatty alcohol sulfates, oil soluble petroleum sulfonates, or preferably mixtures of these emulsifying agents. Such emulsifying agents will comprise from about 1 to 10 weight percent of the total composition.

Thus, emulsifiable concentrates of the present invention will consist of from about 15 to about 50 weight percent active material, about 40 to 82 weight percent solvent, and about 1 to 10 weight percent emulsifier. Other additives such as spreading agents and stickers can also be included.

C. GRANULES AND PELLETS

Granules and pellets are physically stable, particulate composi-compositions containing the active ingredients adhering to or distributed through a basic matrix of a coherent, inert carrier with microscopic dimensions. A typical particle is about 1 to 2 millimeters in diameter. Surfactants are often present to aid in leaching of the active ingredient from the granule or pellet.

The carrier is preferably of mineral origin, and generally falls within one of two types. The first are porous, absorptive, preformed granules, such as preformed and screened granular attapulgite or heat expanded, granular, screened vermiculite. On either of these, a solution of the active agent can be sprayed and will be absorbed at concentrations up to 25 weight percent of the total weight. The second, which are also suitable for pellets, are initially powdered kaolin clays, hydrated attapulgite, or bentonite clays in the form of sodium, calcium, or magnesium bentonites. Water-soluble salts, such as sodium salts, may also be present to aid in the disintegration of granules or pellets in the presence of moisture. These ingredients are blended with the active components to give mixtures that are granulated or pelleted, followed by drying, to yield formulations with the active component distributed uniformly throughout the mass. Such granules and pellets can also be made with 25 to 30 weight percent active component, but more frequently a concentration of about 10 weight percent is desired for optimum distribution. The granular compositions of this invention are most useful in a size range of 15-30 mesh.

The surfactant is generally a common wetting agent of anionic or nonionic character. The most suitable wetting agents depend upon the type of granule used. When preformed granules are sprayed with active material in liquid form the most suitable wetting agents are nonionic, liquid wetters miscible with the solvent. These are compounds most generally known in the art as emulsifiers, and comprise alkylaryl polyether alcohols, alkyl polyether alcohols, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol esters with fatty or rosin acids, fatty alkylol amide condensates, oil solution petroleum or vegetable oil sulfonates, or mixtures of these. Such agents will usually comprise up to about 5 weight percent of the total composition.

When the active ingredient is first mixed with a powdered carrier and subsequently granulated, or pelleted, liquid nonionic wetters can still be used, but it is usually preferable to incorporate at the mixing stage one of the solid, powdered anionic wetting agents such as those previously listed for the wettable powders. Such agents will comprise from about 0 to 2 weight percent of the total composition.

Thus, the preferred granular or pelleted formulations of this invention comprise about 5 to 30 percent by weight active material, about 0 to 5 weight percent wetting agent, and about 65 to 95 weight percent inert material carrier, as these terms are used herein.

D. MICROCAPSULES

Microcapsules consist of fully enclosed droplets or granules containing the active materials, in which the enclosing material is an inert porous membrane, arranged to allow escape of the enclosed materials to the surrounding medium at controlled rates over a specified period. Encapsulated droplets are typically about 1 to 50 microns in diameter.

The enclosed liquid typically constitutes about 50 to 95% of the weight of the entire capsule, and may contain a small amount of solvent in addition to the active materials.

Encapsulated granules are characterized by porous membranes sealing the openings of the granule carrier pores, trapping the liquid containing the active components inside for controlled release. A typical granule size ranges from 1 millimeter to 1 centimeter in diameter. In agricultural useage, the granule size is generally about 1 to 2 ml in diameter. Granules formed by extrusion, agglomeration, or prilling are useful in the present invention as well as materials in their naturally occurring form. Examples of such carriers are vermiculite, sintered clay granules, kaolin, attapulgite clay, sawdust, and granular carbon.

Useful encapsulating materials include natural and synthetic rubbers, cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, polyurethanes, and starch xanthates.

E. IN GENERAL

Each of the above formulations can be prepared as a package containing the herbicide together with other ingredients of the formulation (diluents, emulsifiers, surfactants, etc.). The formulations can also be prepared by a tank mix method, in which the ingredients are obtained separately and combined at the grower site.

In general, an conventional method of application can be used. The locus of application can be soil, seeds, seedlings, or the actual plants, as well as flooded fields. Post-emergent application is preferred. Dusts and liquid compositions can be applied by the use of powder dusters, boom and hand sprayers, and spray dusters. The compositions can also be applied from airplanes as dusts and sprays because they are effective in very low dosages. In order to modify or control the growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions are applied to the soil according to conventional methods and are distributed in the soil to a depth of at least one-half inch below the soil surface. It is not necessary that the phytotoxic compositions be admixed with the soil particles. Instead, these compositions can be applied merely by spraying or spinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations.

The herbicide compositions can also be applied to the soil through irrigation systems. According to this technique, the compositions are added directly to irrigation water immediately prior to irrigation of the field. This technique is applicable in all geographical areas regardless of rainfall, since it permits supplementation of the natural rainfall at critical stages of plant growth. In a typical application, the concentration of the herbicide composition in the irrigation water will range from about 10 to 150 parts per million by weight. The irrigation water can be applied by the use of sprinkler systems, surface furrows, or flooding. Such application is most effectively done before the weeds germinate, either early in the spring prior to germination or within two days after cultivation of the field.

The amount of the present composition which constitutes a herbicidally effective amount depends upon the nature of the seeds or plants to be controlled. The rate of application of active ingredient varies from about 0.01 to about 50 pounds per acre, preferably about 0.1 to about 25 pounds per acre with the actual amount depending on the overall cost and the desired results. It will be readily apparent to one skilled in the art that compositions exhibiting lower herbicidal activity will require a higher dosage than more active compounds for the same degree of control. 

What is claimed is:
 1. A substituted aryloxyphenoxy-propionyl thiourea compound having the formula ##STR4## wherein R₁ is CF₃ or halogen; R₂ is H or halogen; A is CH or N; R₃ and R₄ are each independently hydrogen or lower alkyl, alkenyl or alkynyl groups having up to 5 carbon atoms.
 2. The compound of claim 1 in which R₁ is CF₃.
 3. The compound of claim 1 in which R₂ is chlorine.
 4. The compound of claim 1 in which R₃ and R₄ are both lower alkyl having from 1 to 4 carbon atoms.
 5. The compound of claim 1 in which A is nitrogen.
 6. The compound of claim 1 in which each of R₃ and R₄ are methyl.
 7. A herbicidal composition which comprises a herbicially effective amount of a substituted aryloxyphenoxypropionyl thiourea having the formula ##STR5## wherein R₁ is CF₃ or halogen; R₂ is H or halogen; A is CH or N; R₃ and R₄ are each independently hydrogen or lower alkyl, alkenyl or alkynyl groups having up to 5 carbon atoms and an inert diluent carrier.
 8. The composition of claim 7 in which R₁ is CF₃.
 9. The composition of claim 7 in which R₂ is chlorine.
 10. The composition of claim 7 in which R₃ and R₄ are both lower alkyl having from 1 to 4 carbon atoms.
 11. The composition of claim 7 in which A is nitrogen.
 12. The composition of claim 7 in which each of R₃ and R₄ are methyl.
 13. A method for controlling undesirable weed pests which comprises applying to the locus where control is desired a herbicidally effective amount of a compound having the formula ##STR6## wherein R₁ is CF₃ or halogen; R₂ is H or halogen; A is CH or N; R₃ and R₄ are each independently hydrogen or lower alkyl, alkenyl or alkynyl groups having up to 5 carbon atoms.
 14. The method of claim 13 in which R₁ is CH₃.
 15. The method of claim 13 in which R₂ is chlorine.
 16. The method of claim 13 in which R₃ and R₄ are both lower alkyl having from 1 to 4 carbon atoms.
 17. The method of claim 13 in which A is nitrogen.
 18. The method of claim 13 in which each of R₃ and R₄ are methyl.
 19. A herbicidal composition comprising a herbicidally effective amount of aryloxyphenoxypropionyl thiourea and an inert diluent carrier.
 20. A herbicidal composition of claim 8 in which said compound is N-[2-(4'-(4"-trifluoromethylphenoxy)phenoxy)propionyl]-N'-1,1-dimethylpropargyl thiourea. 